Dryer



Sept. 17, 1968 w. E. BEARCE DRYER 5 Sheets-Sheet 1 Filed Feb. 17, 1966 F I G. l.

F l G. 4.

F I G. 3.

INVENTOR WENDELL E. BEARCE MMFM? ATTORNEYS Sept. 17, 1968 BEARCE DRYER 5 Sheets-Sheet 2 Filed Feb. 17, 1966 as j wm a E INWMWL BY 4440 i M ATTORNEYS Sept. 17, 1968 I w. E. BEARCE 3,401,923

DRYER Filed Feb. 17, 1966 5 Sheets-Sheet 5 FIG. 5.

INVENTOR WEN DELL E. BEARCE ATTOR NEYS United States Patent 3,401,923 DRYER Wendell E. Bearce, St. Clairsville, Ohio, assignor to Wilmot Engineering Company, White Haven, Pa., a corporation of Pennsylvania Filed Feb. 17, 1966, Ser. No. 528,261 10 Claims. (Cl. 263-32) ABSTRACT OF THE DISCLOSURE A dryer for wet granular material comprising a rotatable drum or container into which is fed the wet granular material at its feed end. Heated particles are introduced through the feed end into the wet granular material and mixes with it to transfer heat thereto to dry the material. The drum slopes downwardly and is rotated so as to move the mixture of particles and material in concurrent flow through the drum to a discharge end where the dry material is discharged and the particles are recovered and deposited in a heating chamber or housing where the particles are moved in a direction countercurrent to the flow of the mixed particles and are reheated and reintroduced to the wet granular material at the feed end of the container. A perforated screw conveyor advances the particles through the reheating housing and a fan pulls the heating gases from a heating source located at the feed end of the drum through the advancing particles.

This invention relates to a dryer and more particularly concerns a dryer for drying wet granular material such as Wet coal and the like.

It has been a problem to dry wet fine particles of material such as coal coming from a vacuum filter at 22% to 32% moisture in more or less fiat slabs or globs which may be six inches wide, by twelve inches long, by one-half to two inches thick. Such material is very diificult to handle in a dryer. It sticks to everything it touches and will plug even a vertical chute by gradually building up on the sides of the chute. A vibrating feeder inclined at a normal angle of to degrees from the horizontal is not able to handle this material at all, nor is a screw conveyor.

Any dryer which utilizes a hot air stream to carry and dry fine particles cannot pick up or support such slabs or globs and cannot separate the particles so that the hot gas can contact the particles individually.

Dryers which use rotating drums, or vibrating screens or plates, merely roll such slabs into balls. The outside of these balls becomes excessively dry upon being contacted by hot gases and this produces dust, which is undesirable, and yet the inside stays wet.

Dryers which utilize hot air to dry material having a mixture of coarse and fine particles do not dry the particles evenly. By the time the coarse material is dry, the fines are so dry as to create a danger of explosion.

A number of prior art devices depend on hot air from a furnace to pick up and dry a wet coal feed. But the hot air cannot pick up chunks or lumps of coal and so they merely fall to the bottom of the machine and are not dried. Also, the hot air cannot pick up smaller material of 100 mesh size, for example, which agglomerates and sticks together. The material which the hot air does pick up is heated and carried to a dry collector which takes out the coarse particles. The fine particles are drawn out of the dry collector by a fan and transported to a wet scrubber where the fines are mixed with water and are disposed of in a stream, or deposited on the countryside behind a dam, where it is hoped that the fines will eventually settle out. However, this creates problems of water and stream pollution, and disposing of the fines may be a diflicult problem.

Accordingly, it is an object of this invention to provide a dryer which overcomes the problems of the prior art.

It is another object of this invention to provide a dryer which avoid-s stream pollution and air contamination.

It is another object to provide a dryer which saves space and requires only a low capital expenditure by comparison with previous dryers.

Other objects and advantages of this invention, including its simplicity and economy, as well as the ease with which it may be adapted to existing equipment, will further become apparent hereinafter and in the drawings, in which:

FIG. 1 is a view in perspective of a dryer constructed in accordance with this invention;

FIG. 2 is an elevational view, partly in section and partly schematic, of the dryer shown in FIG. 1;

FIG. 3 is a view in section taken as indicated by the lines and arrows 3-3 which appear in FIG. 2;

FIG. 4 is a view in section taken as indicated by the lines and arrows 4-4 which appear in FIG. 2; and

FIG. 5 is an elevational view, partly in section and partly schematic, of another embodiment of the invention.

Although specific terms are used in the following description for clarity, these terms are intended to refer only to the structures shown in the drawings and are not intended to define or limit the scope of the invention.

Turning now to the specific embodiments of the invention selected for illustration in the drawings, there is shown in FIGS. 1-4 a dryer 11 for drying wet granular material 12. The dryer includes a rotatable container or cylinder 13 having a feed end 14 and a discharge end 15. A feed hopper 16 and vibrating feed chutes 17 are provided for feeding the wet granular material 12 to feed end 14.

A housing 18, having a feed end 21 and a discharge end 22, is adapted to introduce heated particles 23 into Wet granular material 12 to transfer heat to and dry the granulated material while in cylinder 13. Housing 18 feeds particles 23 to feed end 14 of cylinder 13. The particles 23 may be of any shape, for example, they may be balls of steel or of other heat conducting material.

The particles 23 are heated in housing 18. The heating means includes a firing chamber 24 lined with refractory brick 25, and a burner 26 which generates hot gases 27 and directs them through housing 18 to heat the particles therein.

Particles 23 are recycled through cylinder 13. The recycling means includes a lifting chamber 28 at the exit end of cylinder 13 for receiving the particles 23 which have transferred their heat to the granular material and are now cool, and lifters 31 mounted in chamber 28 for elevating the particles to feed end 21 of housing 18.

Air locks 32 limit the amount of air that is sucked into housing 18 from lifting chamber 28, and comprise a num 'ber of panels which revolve around an axis in the manner of a revolving door. 1

An exhaust fan 33 positioned downstream of lifting chamber 28 pulls the hot gases from firing chamber 24 through housing 18. Air locks 32 prevent excess air from lifting chamber 28 from reducing the efficiency of the exhaust fan.

In the embodiment of the invention of FIGS. l4, housing 18 is positioned concentrically within cylinder 13 and rotates therewith. A screw conveyor 34 is mounted within housing 18 for advancing particles 23 from feed end 21 to discharge end 22, and the flights of screw conveyor 34 are perforated near their outer periphery so that the hot gases 27 pass through the particles as they advance along the bottom of housing 18.

A fan protection screen 35 is located at the bottom end of housing 18 and acts as a guard to prevent particles 23 from passing into fan 33.

The discharge end 22 of housing 18 has discharge slots 36 formed therein through which the heated particles are fed into cylinder 13. A cover 37 is positioned around the top and sides of discharge end 22 and covers all but the downwardly-facing slots 36 during rotation of the housing so as to prevent wet granular material 12 from entering housing 18 through the slots.

At the discharge end of cylinder 13, there is a screen section 38 through which the dried granular material 41 is discharged. Particles 23 are too large to pass through the slots in screen section 38, and pass into lifting chamber 28 over an annular ring which forms a dam 42. Dam 42 is high enough that particles 23 pass into chamber 28 free of the granular material which passes through screen 38. Lifters 31 elevate particles 23 to the height of the feed end 21 of housing 18 and drop them through air locks 32 and into housing 18 through feed opening 43.

During operation of the dryer, water vapor is liberated at feed end 14 from the wet granular material 12 by contact with the heated particles 23, and this vapor is disposed of by passing it through a water vapor hood 44 and a discharge duct 45 which may connect with a stack, or may connect directly to atmosphere. A fan may be positioned in duct 45 to assist in pulling the vapor from cylinder 13.

The hot gases 27 lose heat during their passage through housing 18 and are discharged through a discharge duct 46 located at feed end 21. A temperature sensor 47 is positioned in duct 46 and measures the temperature of the cooled gases. Sensor 47 is connected to and actuates a fuel control valve 48 which controls the amount of fuel being fed to the burner 26, thereby controlling the temperature of particles 23.

The dried granular material is discharged at end 15 into a chute 51. A moisture sensor 52 is positioned in chute 51 to measure the moisture content of the dried material, and is connected to a lifting mechanism control 53 that adjusts the height of lifting mechanism 54 which supports one end of the dryer. Sensor 52 thereby controls the slope of cylinder 13 and the moisture content of the dried material. If the moisture content of the dried granular material 41 is too high, moisture sensor 52 signals control 53 to raise lifting mechanism 54. Accordingly, the slope is decreased and the granular material remains in the cylinder longer and more water is evaporated from the material.

If the granular material is too dry, moisture sensor 52 signals control 53 to lower lifting mechanism 54. Accordingly, the slope is increased and the material runs through faster so that less moisture is evaporated.

In addition to being connected to lifting mechanism control 53, or as an alternative to this connection, moisture sensor 52 may be connected to a motor speed control 55 that adjusts the speed of a motor 56 which rotates cylinder 13 through a variable speed reducer 57 and gears 58.

If moisture sensor 52 ascertains that the moisture content of granular material 41 is too high, it signals motor speed control 55 to decrease the rotational speed of motor 56 and cylinder 13 to slow the travel of the material through the cylinder and thereby increase the retention time of the material in cylinder 13 so that more water is evaporated. If moisture sensor 52 ascertains that the moisture content is too low, it signals motor speed control 55 to increase the rotational speed of motor 56 and cylinder 13 to quicken the travel of the mixture through the cylinder and thereby decrease retention time so that less water is evaporated.

A main frame 61 supports the elements of the dryer, including firing chamber 24, water vapor hood 44, exhaust fan 33, motor 56, gears 58, and cylinder roller assemblies 62. Main frame 61 is supported at the feed end of the dryer by a pivot assembly 63 and at the discharge end by lifting mechanism 54.

In operation, wet granular material 12 is introduced 4 into feed hopper 16 and is deflected by vibrating feed chutes 17 into the feed end 14 of cylinder 13 which is being rotated by drive motor 56 through variable speed reducer 57 and cylinder drive gears 58, the cylinder being supported for rotation on cylinder roller assemblies 62.

Cover 37 is supported on main frame 61 by legs 64 that hold the cover stationary and prevent any particles of the wet granulated material 12 from entering housing 18 through discharge slots 36.

Hot gases 27 produced in firing chamber 24 by burner 26 are drawn through screw conveyor housing 1-8 by fan 33, and pass over, around and through the particles 23 to heat them to the desired high temperature. The gases 27 are cooled by this passage through housing 18 and transfer of heat to particles 23, and are discharged to the atmosphere by exhaust fan 33 through a discharge duct 46.

The hot particles 23 are discharged by gravity from discharge end 22 of housing 18 into feed end 14 of cylinder 13 through slots 36. The hot particles 23 mix with wet granular material 12 and transfer heat thereto as the mixture moves down the slope of rotating cylinder 13. The heat converts the water in the wet granular material into water vapor which is discharged through discharge duct 45. The dried mixture falls into the enlarged diameter discharge end 15 and is separated into its components of particles 23 and the now dried granular material 41. The dried granular material 41 passes through the openings in the screen section 38 into discharge chute 51, and the particles 23 flow over darn 42 into lifting chamber 28.

Lifters 31 elevate the particles so that they fall through air locks 32 and feed opening 43 into housing 18. Screw conveyor 34 moves the particles up the slope of housing 18 as they are being heated by the hot gases 27 and then feeds them through discharge slots 36 into feed end 14 of rotating cylinder 13.

The water vapor which is liberated from the wet granular material 12 when it is contacted by and mixed with hot particles 23 is withdrawn from rotating cylinder 13 through water vapor hood 44 and discharge duct 45.

FIG. 5 illustrates another embodiment of the invention wherein the housing for heating the particles is placed outside the rotatable cylinder. As is shown, this form of dryer includes a main frame 71 supported by pivot assembly 72 and lifting mechanism 73.

A rotatable cylinder 74 is supported on main frame 71 by roller assemblies 75 and is rotated by motor 76 through variable speed reducer 77 and drive gears 78.

Wet granular material 12 is introduced into rotatable cylinder 74 through a feed hopper 81, and hot particles 23 are introduced into cylinder 74 through a hopper 82.

Water vapor created by the mixing of the particles 23 and wet granular material 12 is discharged from the dryer through water vapor hood 83 and discharge duct 84.

The mixture of granular material and particles 23 passes through cylinder 74 from feed end 85 to screened discharge end 86 where the now dried granular material 41 passes downwardly through the screen slots into a discharge chute 87, while the particles 23 ride over dam 88 into lifting chamber 91 where they are elevated by lifters 31 and discharged through air locks 32 into a receiving hopper 92. The now cooled particles 23 are transferred from hopper 92 by any suitable mechanism, such as by conveyor 93, to a feed hopper 94 of a housing 95 which includes a screw conveyor 96 that transports the particles from feed end 97 of housing 95 to discharge end 98.

During the passage of particles 23 through housing 95, they are heated by hot gases generated in firing chamber 101. The hot gases are sucked through housing 95 by a fan 102 which is protected from particles 23 by a screen 103.

Since housing 95 is external to drum or cylinder 74, it is rotated by a separate drive mechanism 104.

As to advantages, the dryer of the present invention is 'able to handle sticky, caked or gummy material and provide intimate contact between disparate elements of such material and the particles 23.

The dryer is able to dry materials which are subject to combustion. It can do so because it utilizes a parallel flow principle whereby the material 12 being treated, and the particles 23 fiow together in parallel paths so that the hottest particles come into contact with the wettest material. As the material 12 becomes progressively dryer, the particles 23 in contact therewith become progressively cooler. Accordingly, the dryest material is never contacted by the hottest particles, so that the danger of combustion is avoided.

One of the safety features of the dryer is that the hot gases 27 do not come in contact with the combustible material being treated at any time.

The dryer of this invention eliminates the problems of separating out dust, which problems are inherent in dryers utilizing a hot gas for drying. It does so by providing that the hot gases are never in contact with the treated material and do not have to be separated from that material in expensive, space consuming, high head room, dust recovery apparatus. In conventional apparatus, the drying gas picks up dust from the material being dried, and must be discharged through wet scrubbers in order to remove the dust. The wet dust must be dried, or disposed of as waste. One way of disposing of the wet dust is to deposit it in a pond.

The water vapor escaping from the dryer of this invention has a high velocity only at the feed end 14 of cylinder 113 'where the granular material 12 is at its wettest and the greatest amount of water vapor is generated. However, the water vapor does not pick up any dust from the granular material because it is so wet and heavy.

At the discharge end 15 of cylinder 13, where the granular material is at its driest, comparatively little water is emitted from the granular material. Accordingly, the volume of water vapor created is small and its velocity is too slow to pick up any dust from the dried material and carry it to discharge duct 45.

It is to be noted that the dried material 41 is separated from the source of heat 26 by the length of rotating cylinder .13.

Since no large volumes of air are handled by the dryer, the power consumption is only a small fraction of that consumed by air dryers. The only air required is for the combustion of the fuel in firing chamber 24. The material to be dried is not elevated by air.

The thermal efficiency of the dryer is very high. Clyinder 13 may be insulated externally, and all the hot gases are confined to a relatively small housing 18. Any heat radiating from exterior of housing 18 raises temperature in cylinder 13 and assists drying of wet material. Moreover, the helical path through internal screw conveyor 34 is extremely long so that hot gases 27 become cool during their passage through housing 18 and are discharged at a low temperature through screen 35 into fan 33 and discharge duct 46.

The dryer of the present invention provides a better control of the final moisture content of the granular material since there is no tendency for segregation of particle sizes in the dryer as with dryers employing air to dry the material. Also, there is no tendency to over-dry smaller particles prior to completely drying larger particles. This is very important since the object is to try to reduce the moisture content of the material as much as possible without creating dust.

Although cylinders ;13 and 74 have been shown as being rotatable, they could be fixed in position with rotatable parts therein, such as a paddle mixer, for moving the material along. Also, housings 18 and 95 could be fixed and inside members could move the particles 23, such as rotable screw conveyors.

It is to be understood that the form of the invention herewith shown and described is to be taken as a presently preferred embodiment. Various changes may be made in the shape, size and arrangement of parts. For example, equivalent elements may be substituted for those illustrated and described herein, parts may be reversed, and certain features of the invention may be utilized independently of the use of other features, all without departing from the spirit or scope of the invention as defined in the subjoined claims.

I claim:

1. A dryer for drying wet granular material comprising a container having a feed end and a discharge end, means for feeding wet granular material into said feed end, means for introducing heated particles into said wet granular material to transfer heat to and dry said wet granular material while in said container, and means for recycling said heated particles through said wet granular material in said container, said recycling means includ ing a housing having a feed end and a discharge end, means for separating said particles from said dry granular material and delivering the particles to said housing, and means for heating said particles in the housing, said discharge end of the housing having discharge slots formed therein through which the particles are fed into said container, and a cover positioned around the top and the sides of the housing to cover the slots and prevent said wet granular material from entering the housing through said slots.

2. A dryer for drying wet granular material comprising a container having a feed end and a discharge end, means for feeding wet granular material into said feed end, means for introducing heated particles into said wet granular material to transfer heat to and dry said wet granular material while in said chamber, and means for recycling said heated particles through said wet granular material in said container, said recycling means including a housing having a feed end and a discharge end, means for separating said particles from said dry granular material and delivering the particles to said housing, and means for heating said particles in the housing, and said discharge end of the container includes: a discharge screen section through which the dried granular material is discharged, a lifting chamber for receiving and lifting said particles, and a dam defining one end of the lifting chamber, said particles being adapted to flow over the dam into the lifting chamber free of the granular material.

3. A dryer for drying wet granular material comprising a container having a feed end and a discharge end, means for feeding wet granular material into said feed end, means for introducing heated particles into said wet granular material to transfer heat to and dry said wet granular material while in said container, and means for recycling said heated particles through said wet granular material in said container, said recycling means including a housing having a feed end and a discharge end, means for separating said particles from said dry granular material and delivering the particles to said housing, and means for heating said particles in the housing, the discharge end of the container including a lifting chamber having lifters for elevating said particles to the feed end of the housing and having air lock means at the end of the lifters for limiting passage of air from the lifting chamber to the housing.

4. A dryer for drying wet granular material comprising a container having a feed end and a discharge end, means for feeding wet granular material into said feed end, means for introducing heated particles into said wet granular material to transfer heat to and dry said wet granular material while in said container, and means for recycling said heated particles through said wet granular material in said container, said recycling means including a housing having a feed end and a discharge end, means for separating said particles from said dry granular material and delivering the particles to said housing, and means for heating said particles in the housing, a discharge chute located at the discharge end of the container for receiving the dried granular material, moisture sensing means located in said granular material discharge chute for measuring the moisture of the dried material, a lifting mechanism coupled to the container and adapted to raise and lower one end of the container to change its slope to speed or retard the passage of granular material therethrough, and lifting mechanism control means connected to and actuated by the moisture control means to control the slope of the container to increase its slope so that the granular material passes through faster and thereby is discharged wetter, or to decrease its slope so that the granular material passes through more slowly and is discharged drier.

5. A dryer for drying wet granular material comprising a container having a feed end and a discharge end, means for feeding wet granular material into said feed end, means for introducing heated particles into said feed end to mix with said material to transfer heat to and dry said material, means for moving said particles and material in concurrent flow through the container, means for separating said particles from said material, means for returning said particles to the feed end by moving said particles in a direction countercurrent to the flow of said mixed particles and material, means for reheating said particles during the course of travel from the discharge end to the feed end, whereby the reheated particles are recycled through the container to dry the wet granular material, a discharge chute located at the discharge end of the container for receiving the dried granular material, moisture sensing means located in the discharge chute for measuring the moisture of the dried material, and speed control means coupled to the container for controlling the speed of rotation of the container, said speed control means being actuated by the moisture sensing means.

6. A dryer for drying wet granular material comprising a container having a feed end and a discharge end, means for feeding wet granular material into said feed end, means for introducing heated particles into said feed end to mix with said material to transfer heat to and dry said material, means for moving said particles and material in concurrent flow through the container, a housing having a feed end and a discharge end, said housing being positioned concentrically within the container, means for separating said particles from said materials and delivering the particles to said housing, means for returning said particles to the feed end by moving said particles in a direction countercurrent to the flow of said mixed particles and material, and means for reheating said particles during the course of travel from the discharge end to the feed end, whereby the reheated particles are recycled through the container to dry the wet granular material.

7. The dryer according to claim 6 wherein the means for heating the particles includes a burner located at the discharge end of the housing which directs heat at the advancing particles so as to gradually increase their temperature, and an exhaust fan located at the feed end of the housing for pulling hot gases from the burner through the housing and preventing the hot gases from flowing outside the housing into the container.

8. A dryer for drying wet granular material comprising a container having a feed end and a discharge end, means for feeding wet granular material into said feed end, means for introducing heated particles into said feed end to mix with said material to transfer heat to and dry said material, means for moving said particles and material in concurrent flow through the container, a housing having a feed end and a discharge end, means for separating said particles from said materials and delivering the particles to said housing, means for returning said particles to the feed end by moving said particles in a direction countercurrent to the flow of said mixed particles and material, means for reheating said particles during the course of travel from the discharge end to the feed end, whereby the reheated particles are recycled through the container to dry the wet granular material, a cooled gases discharge duct extending from the feed end of the housing, temperature sensing means located in the discharge duct for measuring the temperature of the cooled gases, and fuel control means actuated by the temperature sensing means to control the means for heating the particles.

9. The dryer according to claim 8, including means for rotating the container.

10. The dryer according to claim 8, wherein said means for returning said particles to the feed end comprises a screw conveyor for advancing said particles through the housing.

References Cited UNITED STATES PATENTS 1,338,731 5/1920 Hutchinson 34-137 1,459,923 6/1923 Nagel 26325 1,534,499 4/1925 Braemer 3450 1,590,339 6/1926 \Vood 263-21 1,614,387 1/1927 Pereda -107 1,965,881 7/1934 Clark et al. 34126 2,092,657 9/ 1937 Smith.

2,484,539 10/1949 Walker 26332 2,592,783 4/1952 Aspegren 165-88 X 2,872,386 2/1959 Aspegren 165-88 X 2,986,457 5/1961 Jones 26333 X 3,013,785 12/1961 King 26333 3,302,937 2/1967 PiXley 26332 FOREIGN PATENTS 1,066,474 10/ 1959 Germany.

FREDERICK L. MATTESON, JR., Primary Examiner.

A. D. HERRMANN, Assistant Examiner. 

